This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We are investigating possible causes of a disease called irritable bowel syndrome (IBS). IBS is a medical condition characterized by abdominal pain, diarrhea and constipation for which there are few effective treatments. We believe that part of the syndrome might be caused by an abnormal response to rectal sensation in the brain. To investigate this possibility we need to take pictures of volunteers 'brains while they receive a mildly painful and discomforting rectal stimulus. The pictures are taken using a magnetic resonance imaging (MRI) machine. The MRI uses a very powerful magnetic field that can detect differences in the structure and function or activity of the brain. Differences between normal subjects and subjects with IBS in the brain response to rectal pressure will help in the guidance of future research and clinical therapy. Each subject will be involved in one experimental session. A balloon that can be inflated with a barostat (air pump) will be inserted into the rectum. Preliminary inflations will be rated for intensity and discomfort to insure that the inflation levels used in the experiment are not overly painful. Subjects will then be positioned in the MRI scanner according to standard procedure. For 45 minutes subjects will rate the intensity of 90 15 second balloon inflations while their brains are scanned. With breaks as needed, each session will last from one to two hours.